Slang for a quick jack off or blow job, where only the zipper is undone, and the person ejaculates.
Mainly slang term, for when one undoes their zipper, allow another to take the penis, and suck on it until the person ejaculates, either into the mouth or on the person's face.
Difference between Zipper Sex and Zipper Dinner, is that for Zipper Dinner, ejaculation must occur.
Noteworthy: Usually performed in public locations, but out of sight, such as in an alley. Usually a paid sexual act, or one that occurs spur of the moment, during a cruising.